NAME
g_filter - frequency filters trajectories, useful for making smooth
movies
VERSION 4.0.1
SYNOPSIS
g_filter -f traj.xtc -s topol.tpr -n index.ndx -ol lowpass.xtc -oh
highpass.xtc -[no]h -nice int -b time -e time -dt time -[no]w -nf int
-[no]all -[no]nojump -[no]fit
DESCRIPTION
g_filter performs frequency filtering on a trajectory. The filter
shape is cos(pi t/A) + 1 from -A to +A, where A is given by the option
-nf times the time step in the input trajectory. This filter reduces
fluctuations with period A by 85%, with period 2*A by 50% and with
period 3*A by 17% for low-pass filtering. Both a low-pass and
high-pass filtered trajectory can be written.
Option -ol writes a low-pass filtered trajectory. A frame is written
every nf input frames. This ratio of filter length and output
interval ensures a good suppression of aliasing of high-frequency
motion, which is useful for making smooth movies. Also averages of
properties which are linear in the coordinates are preserved, since all
input frames are weighted equally in the output. When all frames are
needed, use the -all option.
Option -oh writes a high-pass filtered trajectory. The high-pass
filtered coordinates are added to the coordinates from the structure
file. When using high-pass filtering use -fit or make sure you use a
trajectory which has been fitted on the coordinates in the structure
file.
FILES
-f traj.xtc Input
Trajectory: xtc trr trj gro g96 pdb cpt
-s topol.tpr Input, Opt.
Structure+mass(db): tpr tpb tpa gro g96 pdb
-n index.ndx Input, Opt.
Index file
-ol lowpass.xtc Output, Opt.
Trajectory: xtc trr trj gro g96 pdb
-oh highpass.xtc Output, Opt.
Trajectory: xtc trr trj gro g96 pdb
OTHER OPTIONS
-[no]hno
Print help info and quit
-nice int 19
Set the nicelevel
-b time 0
First frame (ps) to read from trajectory
-e time 0
Last frame (ps) to read from trajectory
-dt time 0
Only use frame when t MOD dt = first time (ps)
-[no]wno
View output xvg, xpm, eps and pdb files
-nf int 10
Sets the filter length as well as the output interval for low-pass
filtering
-[no]allno
Write all low-pass filtered frames
-[no]nojumpyes
Remove jumps of atoms across the box
-[no]fitno
Fit all frames to a reference structure
SEE ALSO
gromacs(7)
More information about GROMACS is available at
<http://www.gromacs.org/>.
Thu 16 Oct 2008 g_filter(1)